Researchers at the University of Glasgow have achieved a major milestone in noninvasive brain imaging, demonstrating for the first time that light can travel completely through an adult human head. Their study, published in Neurophotonics, opens new possibilities for probing deep brain regions using optical methods.
Functional near-infrared spectroscopy (fNIRS), a technique that measures blood absorption of light to infer brain activity, is prized for being low-cost and portable. However, its major limitation has been shallow depth, typically reaching only about 4 centimeters into the brain-insufficient to access deeper structures involved in memory, emotion, or motor control.
In their experiment, the Glasgow team employed a pulsed laser aimed at one side of a volunteer's head and a sensitive detector on the opposite side. Their setup eliminated external light and maximized detection of the extremely faint photon signals that had passed through the skull and brain tissue.
Supporting simulations mirrored the experimental findings, confirming photon travel through the full width of the head. These models also showed that light tends to follow brain regions with lower scattering properties, such as cerebrospinal fluid pathways.
Though still in an early stage-the test required 30 minutes of data collection and was limited to a hairless, fair-skinned participant-this success redefines the limits of optical neuroimaging. It could lead to the development of next-generation fNIRS systems capable of accessing deeper brain regions than currently possible.
Ultimately, such technologies may pave the way for compact, affordable brain imaging devices that could be used outside traditional hospital settings to diagnose strokes, monitor tumors, or assess traumatic brain injuries.
Research Report:Photon transport through the entire adult human head
